Filter apparatus

ABSTRACT

The invention relates to a filter apparatus having a plurality of filter elements (21) which can be accommodated in a filter housing (1) with a filter inlet (11) for fluid to be filtered and a filter outlet (13) for the filtered fluid, wherein during the operation of the device at least one of the filter elements (21) can be backflushed by means of a backflushing device for cleaning its effective surface, which backflushing device includes a pressure control device (7) to support the backflushing, characterized in that the filter elements (21) are each accommodated in an element housing (30), the element housings (30) with the filter elements (21) performing the filtration process are connected to the fluid outlet (13) by their one open end (33) in a fluid conducting manner, and the element housing (30) of the respective backflushable filter element (21) is exclusively connected with its one open end (33) to the pressure control device (7).

The invention relates to a filter device having a plurality of filterelements which can be accommodated in a filter housing with a filterinlet for fluid to be filtered and a filter outlet for the filteredfluid, wherein during the operation of the device at least one of thefilter elements can be backflushed by means of a backflushing device forcleaning its effective filter surface, which backflushing devicecontains a pressure control device to support the backwashing.

Filter devices of this kind are state of the art and are used in anumber of different applications and for the filtration of differentflow-capable media, with different device designs being conceivabledepending on the field of application. Preferred application fields arethe cleaning of fluids, such as hydraulic fluids, lubricants or fuels.Such devices can also be used for water treatment or in conjunction withprocess fluids or working fluids of other kinds. To ensure anuninterrupted operation of the connected system to be supplied with thefiltrate, it is essential to regenerate the filter elements realizingthe filtration in a consecutive manner by means of backflushing, whereinduring respective backwashing phases a partial flow of the filtrateflows through the filter element to be regenerated in the oppositedirection, to remove the dirt from the element and carry it away. Inorder to also be able to remove stubborn contaminants in the backwashingoperation, it is known to realize the backwashing operation not only byemploying the operating pressure or system pressure, but to support thebackflushing operation with a pressure control device.

As related prior art, document WO 2012/079661 A1 discloses a filterdevice of the type described above. The pressure control device has ahydropneumatic piston accumulator, the accumulator piston of which formsthe mobile separating element between a gas side and a fluid side, whichis connected to the filtrate side in the filter housing of the filterdevice. The filter elements are arranged rotatable in the filter housingin such a way that a filter element to be regenerated can be aligned bymeans of its raw side with a backflushing cutlet, on which abackflushing valve is located. In order to trigger the backflushingoperation for this filter element, the backflushing valve is opened, sothat for the backflushing operation the volume of the fluid side withthe accumulator pressure of the piston accumulator as pressure gradientis available for removing the contaminants.

Given this prior art, the invention addresses the problem of providing afilter device which is distinguished by particularly advantageousoperational behavior.

According to the invention, this problem is solved by means of a filterdevice having the features of claim 1 in its entirety.

According to the characterizing part of claim 1, a significant featureof the invention is that the filter elements are respectivelyaccommodated in an element housing, that the element housings with thefilter elements realizing the filtration operation with their one openend are connected in a fluid-conducting manner to the filter outlet andthat the element housing of the respective backflushable filter elementwith its one open end is connected only to the pressure control device.With this encapsulation of the filter elements formed by the elementhousings, the pressure of the pressure control device supporting thebackflushing operation acts only on the element to be regenerated whichis located in the backflushing position. The filter elements realizingthe filtration operation thus remain entirely unaffected by thebackflushing pressure of the pressure control device, so that thesefilter elements realize in a normal manner the filtration operation alsoduring backflushing phases under the influence of the system pressure,while the backflushing operation is able to be realized with arelatively higher backflushing pressure permitting a particularlyeffective dirt removal.

In advantageous exemplary embodiments, the respective element housingsare formed from a hollow cylinder with a closed lateral surface, withthe other free end of the element housings having an opening delimitedby the respective accommodated filter element. In this regard, thearrangement can be such that the filter element adjoins the opening insuch a way that said opening forms a fluid connection to the innercavity of the filter element surrounded by the filter medium.

The respective filter element can particularly advantageously be formedconical and have its smallest diameter in the direction of the pressurecontrol device. Such filter elements, also known as filter candles, arepreferably known slotted sieve tube filter elements.

The arrangement can advantageously be such that the flow chamber betweenthe element housing and the accommodated filter element expandsconically in the direction of the pressure control device, with the freecross section of the flow chamber at the top end of the respectivefilter element amounting to 50 to 120%, preferably 100%, of the inletsurface of the element cap of the filter element. This design results ina particularly advantageous flow of the fluid current, so that evenstubborn contaminants can be removed in the backflushing operation.

In preferred exemplary embodiments, all filter elements with theirelement housings are mounted at the end side in rotary receptacles whichcan be moved from a filtration position into a backflushing position andback to a filtration position by means of a rotary drive, preferably ina consecutive manner. For the individual filter elements a rapid andreliable change of operation type between filtration and backflushingcan thus be obtained.

The filter elements realizing the filtration operation canadvantageously be flowed through from the inside to the outside andattached at the base to a common-to-all unfiltrate chamber in the filterhousing, into which the filter inlet opens, and in the case of a closedhead end of the filter element the flow chamber located on the outsidethereof opens, via the top open end of the element housing, into acommon filtrate chamber, which is connected to the filter outlet.

In this arrangement the respective filter element realizing thebackflushing operation is flowed through from the outside to the insideand is connected with its element housing at the head to the pressurecontrol device and is connected in a fluid-conducting manner at the baseto a dirt discharge valve via the free element end.

Particularly advantageously, the rotary receptacles which can be pivotedby means of the rotary drive with the filter elements with their elementhousings can be accommodated concentric and with a definable spacing inthe filtrate chamber of the filter housing. With such an arrangement ofthe filter elements in the manner of an element turret a particularlycompact filter device can realize high filter performance.

The pressure control device can particularly advantageously have anaccumulator part with a pressure chamber that can be filled with aworking gas and a fluid chamber accommodating a backflush volume. Thismakes it possible to provide, a relatively little constructive expense,a fluid volume which is sufficiently large for an optimal backflushingoperation with the desired pressure level.

In particularly advantageous exemplary embodiments, the accumulator partis formed as a piston accumulator, wherein a mobile accumulator pistonis arranged for a media separation between the working gas located inthe pressure chamber and the fluid.

The arrangement can advantageously be such that, between the pressurecontrol device and the filtrate chamber with the rotary receptacles, aseparating wall is drawn in the filter housing, with a throttle point,which in a fluid-conducting manner connects the one bottom pistonchamber of the piston accumulator formed with the accumulator piston tothe filtrate chamber. The fluid side of the piston accumulator can thusbe automatically filled with a filtrate volume during the phases ofnormal filtration operation via the throttle point, which filtratevolume is available for a subsequent backflushing operation, in whichthe accumulator piston is driven into the gas side by means ofintroduction of a pressure medium, such as compressed air, in order todrive out the collected fluid volume from the fluid side of theaccumulator.

The invention is explained in detail below with reference to anexemplary embodiment depicted in the drawings, in which:

FIG. 1 shows a depiction, cut open in a perspective oblique view and inthe longitudinal direction, of an exemplary embodiment of the filterdevice according to the invention and

FIG. 2 shows a longitudinal section of the exemplary embodiment, whereina top housing cover, a dirt release valve and the motor of a rotarydrive are omitted.

In the figures, the housing of the depicted exemplary embodiment of thefilter device according to the invention is identified as a whole withthe reference numeral 1. The housing 1 is formed in three parts andconsists of a base part 3, a central part 5 and a top accumulator part7, which, sealed in a fluid-tight manner, are screwed to each other. Thetop accumulator part 7 is closed in a fluid-tight manner at the top endby means of a housing cover 9 shown only in FIG. 1. The parts 3, 5 and 7each comprise a circular cylindrical section of the housing interior.The base part 3 has, in the vicinity of its closed bottom end, a filterinlet 11 for fluid to be filtered and, opposite the filter inlet 11 andoffset upwards relative thereto, a filter outlet 13 for the filteredfluid. Diametrically opposite the filter inlet 11 on the base part 3there is also a dirt outlet 15, by means of which in a backflushingoperation the respective backflushing fluid volume can be carried out ofthe device via a connected dirt release valve 17. The dirt release valve17 is formed by a motorized valve of standard construction.

In a manner corresponding to the mentioned device (WO 2012/079661 A1)corresponding to the prior art, in the interior, which is comprised ofthe base part 3 and of the central part 5 together, a rotary drive isprovided, with rotary receptacles 19, which with filter elements 21mounted thereon form an element turret. The filter elements 21 formedfrom conical filter candles, in particular in the form of so-calledslotted sieve tube filter elements, are grouped along a circular arcinside the filter housing 1 about the vertical axis, as in thementioned, known solution. For a gradual rotational movement of thefilter elements 1 about the vertical axis, the rotary receptacles 19 areconnected via a drive shaft 23 to a drive motor 25 (hydraulic orelectric) which is only depicted in FIG. 1, which generates rotarymovements of the shaft 23 in a step by step manner in order to rotatethe rotary receptacles 19 into rotary positions in a gradual manner, inwhich rotary positions the rotary receptacles 19 with the filterelements 21 realizing the filtration are respectively aligned with anunfiltrate chamber 47, into which the fluid inlet 11 opens, and thatrotary receptacle 19 with the filter element 21 provided for thebackflushing is aligned with a dirt removal channel 29 in the base part3, which leads to the dirt outlet 15.

Each of the filter elements 21 is accommodated in an element housing 30,the main part of which is formed by a hollow cylinder 31 with a closedlateral surface, which extends between a top open end 33 and a bottomopen end 35 of the element housing 30. At the top open end 33 arespective annular body 37 is located on the end of the hollow cylinder31, which annular bodies are connected via a screw 39 to a support 41forming a coaxial extension of the drive shaft 23. At the bottom openend 35 of the element housings 30 filter element caps 43 (FIG. 2) areprovided, which are each connected in a fluid-tight manner with theassigned rotary receptacle 19.

In this arrangement the inner filter cavity 45 of the filter elements 21realizing the filtration is connected via the bottom open end 35 to theunfiltrate chamber 47, into which the fluid inlet 11 opens. Thefiltration thus takes place from the inner cavity 45, which is closed atthe top end by means of an end body 46, towards the outside through thefilter elements 21, so that the flow chamber 49 between the elementhousing 30 and the outside of the accommodated filter element 21 formsthe respective clean side, with the flow chamber 49 which tapersconically upwards being connected via the top open end of the elementhousings 30 formed by the annular bodies 37 to a common filtrate chamber51, to which the fluid outlet 13 is in turn connected.

The housing central part 5 has a separating wall 53 on the top endforming the transition to the accumulator part 7. In this separatingwall, at a point which is aligned with the respective filter element 21provided for a backflushing operation, there is a passage 55. Via thismeans, the pressure chamber 57 of the accumulator part 7 adjoining theseparating wall 53 is connected, via the top open end 33 of the elementhousing 30 containing the filter element 21 to be backflushed, to theflow chamber 49 on the outside of this filter element 21. This pressurechamber 57 is additionally connected via a throttle point 59 located inthe separating wall 53 to the top region 61 of the filtrate chamber 51.As mentioned and as depicted only in FIG. 1, the top end of theaccumulator part 7 is closed by means of a cover part 9. With a freelymovable accumulator piston 63 which is longitudinally displaceable inthe accumulator part 7, the accumulator part 7 thus forms a pistonaccumulator, in which the pressure chamber 57 located beneath the piston63 forms the fluid side and the chamber 65 located between the piston 63and the cover part 9 forms the gas side, which can be filled via aconnection 67 located in the cover part 9 with a working gas, such ascompressed air. For this purpose, connected to the connection 67 thereis a pressure supply device which is not depicted in detail in thedrawings and which corresponds to the prior art, as is provided in thementioned, known filter device (WO 2012/079661 A1) and which comprises avalve device which makes it possible to supply the chamber 65 withcompressed air via a compressed air line or to block the compressed airsupply, while the chamber 65 is connected to the environment via afilter/throttle device.

In this arrangement the pressure chamber 57 forming the fluid side ofthe piston accumulator formed in the accumulator part 7 can be filledwith filtrate via the throttle point 59, at which the system pressure ofthe filtrate chamber 51 is applied, with the accumulator piston 63moving upwards with an aerated gas-side chamber 65. In order to initiatea backflushing operation when the filter element 21 is aligned with thebackwashing position, as is the case of the filter element 21 visible onthe right in the figures, the gas-side chamber 65 of the pistonaccumulator is charged with compressed air to a pressure level whichcorresponds to the desired backflushing pressure. With the now openeddirt release valve 17 the accumulator piston 63 drives the fluid volumecollected in the chamber 57 as a backflushing volume through the passage55 and the top open end 33 of the element housing 30 located in thebackflushing position into the flow chamber 49 on the outside of thefilter element 21, so that said filter element is flowed through underthe backflushing pressure from the outside to the inner cavity 45.

In this backflushing operation, which occurs with backflushing pressuresupplied from the piston accumulator, which can be selectedsignificantly higher than the system pressure, even stubborncontaminants are removed to be carried off via the bottom open end 35 ofthe corresponding element housing 30 and via the removal channel 29. If,after the backflushing is complete, the dirt removal valve 17 is closedand the gas-side chamber 65 above the accumulator piston 63 is againaerated towards the environment via a throttle, another filling of thefluid-side chamber 57 from the filtrate chamber 51 occurs via thethrottle point 59 due to the system pressure, while the filter elements21 not set to the backflushing position realize the filtration. Becausethese filter elements 21 are completely separated by their elementhousing 30 from the pressure chamber 57 of the piston accumulatorconducting the backflushing pressure, the filtration in the case of thenot backflushed filter elements 21 occurs in an entirely undisturbedmanner and without any disturbance from the backflushing pressure actingon the backflushed filter element 21.

The support of the backflushing operation by the pressure control couldalso take place without the media separation formed by the accumulatorpiston 63 of the accumulator part 7 in such a way that the working gasof the accumulator part 7 acts on the fluid directly. For this purposethe accumulator piston 63 must be removed from the chamber 57 of theaccumulator housing and directly connected to an external pressuresource, such as a nitrogen source, which, controlled by a valve devicewhich is not depicted in detail, delivers defined pressure volumes intothe chamber 57.

1. A filter device having a plurality of filter elements (21) which canbe accommodated in a filter housing (1) with a filter inlet (11) forfluid to be filtered and a filter outlet (13) for the filtered fluid,wherein during the operation of the device at least one of the filterelements (21) can be backflushed by means of a backflushing device forcleaning its effective filter surface, which backflushing devicecontains a pressure control device (7) to support the backwashing,characterized in that the filter elements (21) are respectivelyaccommodated in an element housing (30), in that the element housings(30) with the filter elements (21) realizing the filtration operationwith their one open end (33) are connected in a fluid conducting mannerto the filter outlet (13), and in that the element housing (30) of therespective backflushable filter element (21) with its one open end (33)is connected only to the pressure control device (7).
 2. The filterdevice according to claim 1, characterized in that the respectiveelement housings (30) are formed from a hollow cylinder (31) with aclosed lateral surface and at their other free end have an opening (43)delimited by the respective accommodated filter element (21).
 3. Thefilter device according to claim 1, characterized in that the respectivefilter element (21) is formed conical and has its smallest diameter inthe direction of the pressure control device (7).
 4. The filter deviceaccording to claim 1, characterized in that the flow chamber (49)between the element housing (30) and the accommodated filter element(21) expands conically in the direction of the pressure control device(7) and in that the free cross section of the flow chamber (49) at thetop end of the respective filter element (21) amounts to 50 to 120%,preferably 100%, of the inlet surface of the element cap (43) of thefilter element (21).
 5. The filter device according to claim 1,characterized in that all of the filter elements (21) with their elementhousings (30) are mounted at the end in rotary receptacles (19), whichcan be moved from a filtration position into a backflushing position andback to a filtration position by means of a rotary drive (25),preferably in a consecutive manner.
 6. The filter device according toclaim 1, characterized in that the filter elements (21) realizing thefiltration operation are respectively flowed through from the inside tothe outside and are connected at the base to a common unfiltrate chamber(47) in the filter housing (1), into which the filter inlet (11) opens,and in that in the case of a closed head end (46) of the filter element(21), the flow chamber (49) located on the outside thereof opens, viathe top open end (35) of the element housing (1), into a common filtratechamber (51), which is connected to the filter outlet (13).
 7. Thefilter device according to claim 1, characterized in that the respectivefilter element (21) realizing the backflushing operation is flowedthrough from the outside to the inside and is connected with its elementhousing (30) at the head side to the pressure control device (7) and isconnected in a fluid-conducting manner at the base side via the freeelement end (35) to a dirt release valve (17).
 8. The filter deviceaccording to claim 1, characterized in that the rotary receptacles (19)which can be pivoted by means of the rotary drive (25) with the filterelements (21) together with their element housings (30) are accommodatedconcentric and with a definable spacing in the filtrate chamber (51) ofthe filter housing (1).
 9. The filter device according to claim 1,characterized in that the pressure control device has an accumulatorpart (7) with a pressure chamber (65) which can be filled with workinggas and a fluid chamber (57) accommodating a backflushing volume. 10.The filter device according to claim 1, characterized in that theaccumulator part (7) as a piston accumulator is formed with anaccumulator piston (63) forming a mobile separating element between thepressure chamber (65) and the fluid chamber (57).
 11. The filter deviceaccording to claim 1, characterized in that, between the pressurecontrol device (7) and the filtrate chamber (51) with the rotaryreceptacles (19), a separating wall (63) is drawn in the filter housing(1) with a throttle point (59), which connects in a fluid-conductingmanner the one bottom piston chamber (57) of the piston accumulatorformed with the accumulator piston (63) to the filtrate chamber (51).